The present disclosure relates to additive manufacturing and in particular to a method of fabricating objects via additive manufacturing using photoredox catalysts to achieve metal free photoregulated radical polymerization.
Additive manufacturing is generally a process in which three-dimensional (3D) objects are fabricated based on computer models of the objects. These processes are used in various fields, such as design-related fields for purposes of visualization, demonstration and mechanical prototyping.
3D printing is one example of additive manufacturing. Methods of 3D printing include fused deposition modeling (FDM) and selective laser sintering (SLS). The materials used in 3D printing have typically been polymers; common examples include acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polyamides, polyether ether ketone (PEEK) and thermoplastic polyurethane (TPU).
There are many factors to consider when selecting a 3D printing method and building material, for example, the melt flow rate of the polymer and the solid state properties of the fabricated object.
In FDM, molten polymer filament is extruded from an extrusion nozzle to build the fabricated article layer by layer. The important requirements for the polymer when used in SLS are: good melt flow rates, relatively low melting temperature, good adhesion and good mechanical properties after cooling. ABS is currently the standard material for most applications, however, ABS derived articles made via additive manufacturing suffer from poor physical properties, at least in part because these parts are effectively formed from tens to hundreds of weld lines and ABS weld lines are known to have poor physical properties. Also, fabricating with ABS involves formation of fumes, requiring a well-ventilated area.
In SLS, polymer powder, for example polyamide, TPU, or PEEK, is used. The powder is melted during the sintering process, and the viscosity of the melt and the crystallization temperature can cause the fabricated article to become warped. Further, weak bonding, moisture absorption, and low powder recyclability have been cited as drawbacks of SLS using known polymer feed stocks. Adding additives, such as fillers, has been attempted to address these drawbacks, but this has been met with limited success due to the high viscosity of the polymers—high viscosity prevents uniform loading of the additives to the polymer.
An improved additive manufacturing process is desired to produce fabricated articles having good solid state properties. A method of fabricating objects via additive manufacturing using photoredox catalysts to achieve metal free photoregulated radical polymerization is desired.